French beans are a little trickier to grow than runner beans, but they are arguably more tasty. There is huge variety available – green, purple, flecked, cream – and they are quite versatile. Immature french bean pods are excellent to eat whole, while the beans inside larger pods (often called haricot beans) are also very tasty. Climbing french beans make a very attractive addition to the summer veggie patch.
There are two types of french bean – climbing and dwarf. Dwarf beans grow just 45cm tall and are surprisingly prolific for a small plant. Climbing french beans grow up to 6-8ft tall and produce a lot more beans in the same footprint (important if you don't have much space - you get more bang for your buck). Seeds can be sown direct in the soil or in module trays ready for transplanting - we find the module tray approach better as slugs always seem to get the tiny seedlings when we sow them direct! There’s no point in sowing too early as they will be ready to transplant when the weather outside is too cold for them. Sow two seeds per pot 5cm deep in late April or early May. Sow again in July for a late summer crop.
Plant out when the seedlings are 8-10cm tall following a period of hardening off. Add some well-rotted compost to the holes as you plant out. A bamboo wigwam or double row of canes is the best support structure – we sometimes put runner and french beans in to the same wigwam row. Put three or four beans at the base of each bamboo leaving 30cm between the canes. Plant dwarf varieties in blocks so that they provide each other with shelter and support – leave about 15cm between plants. Hoe around the plants regularly to suppress weeds. Water regularly in dry weather particularly when the flowers start to form. Mulch around the plants if it’s very dry.
It takes 2-3 months for the French bean to produce its first harvest. Harvest from June to October. Start harvesting when the pods are about 10cm long. The more you pick, the more it will churn out. A plant will continue to pod for nearly two months if you keep picking – so keep doing so, even if you are fed up to the back teeth with beans (freeze them, you won’t be so fed up of them in mid winter!). A neat trick is to apply a liquid feed (e.g. comfrey tea) when the plant has finished harvesting to promote a second crop.
French beans are susceptible to late frosts – cover young plants with fleece if frost is forecast. Slugs are a problem for seedlings – seems they absolutely love them. Bean seed fly can be an issue – these are soil living grubs that damage seeds and seedlings.